The aggressive invasion of most aquatic systems with the alien, invasive species water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach has now become a ubiquitous occurrence. Little is known about the implications of this invasion on aquatic biodiversity. In this study, we examined the impacts of water hyacinth, Eichhornia crassipes on the abundance and diversity of macroinvertebrates in Awba reservoir. The abundance and diversity of macroinvertebrate assemblages associated with water hyacinth mats and two other waterweeds, Acroceras zizaniodes and Persicaria senegalense from two sampling stations were determined and compared. In all, a total of 18 different genera consisting of Gastropoda (5), Odonata (2), Coleoptera (4), Rotifera (1), Arachnida (1), Hemiptera (3), Nematoda (1) and Annelida (1) were recorded. The abundance, richness and diversity were tested in several ways. Shannon-Weiner’s index (H) was higher under Acroceras zizaniodes and Persicaria senegalense while Margalef’s index (d) was higher under water hyacinth. Student’s test conducted revealed a significant difference between diversity of invertebrates under Acroceras zizaniodes and Persicaria senegalense vis-a-vis under water hyacinth (P< 0.05). This study showed that water hyacinth mats provide exciting microhabitats for a variety of invertebrate fauna, support higher diversity of organisms and the overall ecology of infested ecosystems can be altered by their invasions.